In-situ solvothermal processing of polycaprolactone/hydroxyapatite nanocomposites with enhanced mechanical and biological performance for bone tissue engineering

The interest in biodegradable polymer-matrix nanocomposites with bone regeneration potential has been increasing in recent years. In the present work, a solvothermal process is introduced to prepare hydroxyapatite (HA) nanorod-reinforced polycaprolactone in-situ. A non-aqueous polymer solution containing calcium and phosphorous precursors is prepared and processed in a closed autoclave at different temperatures in the range of 60–150 °C. Hydroxyapatite nanorods with varying aspect ratios are formed depending on the processing temperature. X-ray diffraction analysis and field-emission scanning electron microscopy indicate that the HA nanorods are semi-crystalline. Energy-dispersive X-ray spectroscopy and Fourier transform infrared spectrometry determine that the ratio of calcium to phosphorous increases as the processing temperature increases. To evaluate the effect of in-situ processing on the mechanical properties of the nanocomposites, highly porous scaffolds (>90%) containing HA nanorods are prepared by employing freeze drying and salt leaching techniques. It is shown that the elastic modulus and strength of the nanocomposites prepared by the in-situ method is superior (∼15%) to those of the ex-situ samples (blended HA nanorods with the polymer solution). The enhanced bone regeneration potential of the nanocomposites is shown via an in vitro bioactivity assay in a saturated simulated body fluid. An improved cell viability and proliferation is also shown by employing (3-(4,5- dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide) (MTT) assay in human osteosarcoma cell lines. The prepared scaffolds with in vitro regeneration capacity could be potentially useful for orthopaedic applications and maxillofacial surgery

Thermally-activated shape memory effect on biodegradable nanocomposites based on PLA/PCL blend reinforced with hydroxyapatite

[EN] In this work, the effect of the addition of different amount of nanosized hydroxyapatite (nHA) on the shape memory behavior of blends based on poly (lactic acid) (PLA) and poly (epsilon-caprolactone) (PCL) has been studied. In particular PLA/PCL blend with 70 wt % PLA has been reinforced with 0.5, 1 and 3 wt % nHA. Moreover, the relationship between the morphology and the final properties of the nanocomposites has been investigated by field emission scanning electron microscopy, confocal Raman spectroscopy and atomic force microscopy. In particular, PeakForce has been used to study quantitative nanomechanical properties of the multifunctional materials leading to conclusion that nHA increase the phase separation between PLA and PCL as well as act as reinforcements for the PCL-rich phase of the nanocomposites. Furthermore, excellent thermally-activated shape memory response has been obtained for all the nanocomposites at 55 degrees C. Finally, the disintegration under composting conditions at laboratory scale level was studied in order to confirm the biodegradable character of these nanocomposites. Indeed, these materials are able to be used for biomedical issues as well as for packaging applications where both thermally-activated shape memory effect and biodegradability are requested.Authors thank the Spanish Ministry of Economy, Industry and Competitiveness, MINEICO, (MAT2017-88123-P) and the Regional Government of Madrid (S2013/MIT-2862) for the economic support. M.P.A. and L.P. acknowledge the Juan de la Cierva (FJCI-2014-20630) and Ramon y Cajal (RYC-2014-15595) contracts from the MINEICO, respectively. The authors also thanks CSIC for the I-Link project (I-Link1149).Peponi, L.; Sessini, V.; Arrieta, MP.; Navarro-Baena, I.; Sonseca Olalla, Á.; Dominici, F.; Giménez Torres, E.... (2018). Thermally-activated shape memory effect on biodegradable nanocomposites based on PLA/PCL blend reinforced with hydroxyapatite. Polymer Degradation and Stability. 151:36-51. https://doi.org/10.1016/j.polymdegradstab.2018.02.019S365115

Syntheses of hydroxyapatite from natural sources

Waste materials from natural sources are important resources for extraction and recovery of valuable compounds. Transformation of these waste materials into valuable materials requires specific techniques and approaches. Hydroxyapatite (HAp) is a biomaterial that can be extracted from natural wastes. HAp has been widely used in biomedical applications owing to its excellent bioactivity, high biocompatibility, and excellent osteoconduction characteristics. Thus, HAp is gaining prominence for applications as orthopaedic implants and dental materials. This review summarizes some of the recent methods for extraction of HAp from natural sources including mammalian, aquatic or marine sources, shell sources, plants and algae, and from mineral sources. The extraction methods used to obtain hydroxyapatite are also described. The effect of extraction process and natural waste source on the critical properties of the HAp such as Ca/P ratio, crystallinity and phase assemblage, particle sizes, and morphology are discussed herein

Calcified Algae for Tissue Engineering.

This book presents the latest advances in marine structures and related biomaterials for applications in both soft- and hard-tissue engineering, as well as controlled drug delivery

Review of nanomaterials in dentistry: interactions with the oral microenvironment, clinical applications, hazards, and benefits.

Interest in the use of engineered nanomaterials (ENMs) as either nanomedicines or dental materials/devices in clinical dentistry is growing. This review aims to detail the ultrafine structure, chemical composition, and reactivity of dental tissues in the context of interactions with ENMs, including the saliva, pellicle layer, and oral biofilm; then describes the applications of ENMs in dentistry in context with beneficial clinical outcomes versus potential risks. The flow rate and quality of saliva are likely to influence the behavior of ENMs in the oral cavity, but how the protein corona formed on the ENMs will alter bioavailability, or interact with the structure and proteins of the pellicle layer, as well as microbes in the biofilm, remains unclear. The tooth enamel is a dense crystalline structure that is likely to act as a barrier to ENM penetration, but underlying dentinal tubules are not. Consequently, ENMs may be used to strengthen dentine or regenerate pulp tissue. ENMs have dental applications as antibacterials for infection control, as nanofillers to improve the mechanical and bioactive properties of restoration materials, and as novel coatings on dental implants. Dentifrices and some related personal care products are already available for oral health applications. Overall, the clinical benefits generally outweigh the hazards of using ENMs in the oral cavity, and the latter should not prevent the responsible innovation of nanotechnology in dentistry. However, the clinical safety regulations for dental materials have not been specifically updated for ENMs, and some guidance on occupational health for practitioners is also needed. Knowledge gaps for future research include the formation of protein corona in the oral cavity, ENM diffusion through clinically relevant biofilms, and mechanistic investigations on how ENMs strengthen the tooth structure